How old is your current garden?
I have a few beds around the old house site that I've been working in with varying degrees of success for 11 years. I also have a big perennial bed that's about 35' x 90' that's turning 5 this year. It's matured much faster than the other beds because it's not sloped and doesn't have tree roots in it. Then there's the brand new beds around the old house site.
I am curious to know how old your gardens are and how much they've changed since their inception.